Magnetic ink character recognition (MICR) characters may be printed on a front surface of a medium such as a bill or a check. Such MICR characters are read by a magnetic ink reader as follows. When the medium is inserted into the reader, a magnet magnetizes the MICR characters. Then, an MICR head, which is a magnetic detection head, detects a residual magnetic field generated by residual magnetism of the MICR characters, and identifies the MICR characters from a magnetic property or a magnetic pattern of the detected magnetic field. From the MICR characters, bills and checks can be distinguished.
Such a magnetic ink reader is incorporated in an ATM or a POS printer 100 as illustrated in FIG. 1, for example. In FIG. 1, P represents a sheet-like medium such as a bill or a check, and K represents a conveyance path of the medium P. FIG. 2 illustrates an example of the medium P. The medium P includes a sheet-like medium body Pa. Characters Pb and MICR characters Pc are printed on the medium body Pa by normal ink and magnetic ink, respectively.
In the printer 100, a magnet 101, an MICR head 102, a feed roller 103 and a pinch roller 104, and an inkjet head 105 and a platen 106 are arranged along the conveyance path K from the left side in FIG. 1. In addition, the printer 100 is provided with a motor 110 configured to drive the feed roller 103 and a gear mechanism 111 configured to transmit torque of the motor 110.
As the magnet 101, a powerful permanent magnet is used to stably magnetize the MICR character Pc. The magnetic field of the magnet 101 has such a property that lines of magnetic force generated from an N pole cause the side surface of the magnet to turn around and become an S pole. Therefore, the magnetic force is the strongest near the magnet 101. Further, the magnet 101 and the MICR head 102 are provided corresponding to the position of the MICR character Pc of the medium P to be conveyed on the conveyance path K.
The printer 100 performs reading by magnetizing the MICR character Pc and detecting the residual magnetic field. In such a printer 100, since reading the MICR character Pc is required to be accurate, magnetization is also required to be performed accurately.
In order to stably magnetize the MICR character Pc, the MICR character Pc is passed in the vicinity of the magnet 101 to magnetize the MICR character with a powerful magnetic force. Since the magnet force in the magnetic field varies greatly depending on position, the relative position between the MICR character Pc and the magnet 101 needs to be adjusted with high accuracy.
However, since the motor 110 configured to convey the medium P is in the vicinity of the magnet 101, vibration of the motor 110 may be transmitted to the magnet 101 or the MICR head 102. When the vibration is transmitted to the magnet 101, the relative position between the magnet 101 and the MICR character Pc fluctuates, and a magnetizing force with respect to the MICR character Pc also sometimes fluctuates. Since the fluctuation of the magnetizing force appears as fluctuation in the magnetic property or the magnetic pattern to be detected by the MICR head 102, the fluctuation has an impact on reading accuracy.
The magnet 101 with a powerful magnetic force may be used to offset the fluctuation. However, since the distance between the magnet 101 and the MICR head 102 is about 4 to 5 cm, the magnetic force of the magnet 101 may affect the reading accuracy of the MICR head 102.
Therefore, there is a need for an apparatus which is capable of reading magnetic ink to be printed on a medium with high accuracy.